The present invention relates to footwear and outerwear heaters, and, more particularly, to wiring and heating element configurations for footwear and outerwear heaters.
There are numerous devices for heating shoes, cold-weather boots, ski boots and the like (collectively and generically referred to as "shoes" or "footwear"). Footwear heating devices generally include a heating element embedded or positioned within an insole. The heating element is connected by a cable or cord to a power supply, such as a battery pack. Most often, the power supply is mounted on the outside of the shoe or attached to the clothing of the person wearing the shoe. Heating devices that are similar to those used in footwear may also be fitted in outerwear such as ski jackets, parkas, and snowsuits.
Although present footwear and outerwear heaters are functional, they have several shortcomings. Prominent among these is that most footwear heaters have unacceptably short commercial lifetimes due to failures in their electrical systems. Each time a wearer puts on a shoe, he or she must route the cord connecting the heating element to the power supply out of the shoe to the location of the power supply. Then, the cord must be connected to the battery. The required routing and connecting causes the cord to be repeatedly bent and stretched. Each time the cord is bent or stretched the wire within it is subjected to tensile forces. Often these forces are sufficiently strong to fracture the wire, resulting in an open-circuit condition. Once the wire in the cord is fractured, the cord must be replaced or, if possible, repaired.
The points at which the cord is attached to the heating element are also subject to repeated bending and pulling. The bending and pulling can cause a fracture of the solder joint connecting the cord to the heating element. As with the wire in the cable, when the solder joint is fractured an open circuit condition is created. Again, a fracture or disconnection at the joint with the heating element requires replacement or repair of the heater.
Another deficiency of presently available heating elements relates to controlling the amount of heat generated by the heater. In most heaters, heat output is controlled by adjusting the current flowing through the heating element with a potentiometer or rheostat, While variable resistance devices provide some control of heat output, more precise control is desired.
Accordingly, there is a need for improved cables and heating elements for footwear and outerwear heaters.